Cash, Cash Equivalents and Investments - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents maturities	90 days
Investment of cash equivalents are redeemable upon demand using amortized cost method	$ 1.00
Investment in money market funds restricted by investment in short term securities, percentage	100.00%
Federal Deposit Insurance Corporation Insured amount	$ 250
Cash	8,625	$ 19,731
Cash equivalents	4,262	701
Cash and cash equivalents in foreign bank	1,400	500
Short-term investments	$ 21,428	$ 39,577
Short-term investments, maturities	90 days
Net unrealized gains	$ 6
Percentage of investment in bond protected by bond default insurance	9.00%	5.00%
Pre-refunded Municipal Bonds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments	$ 7,400	$ 5,200
Corporate Bonds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments	4,200	7,200
U.S. Government Agency Bonds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments	7,700	13,500
Certificates of Deposit [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments	$ 2,100	11,800
Mutual Funds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments		$ 2,000